Palladium-gold catalysts are known. They are used in acetoxylation. For instance, the oxidation of ethylene in the presence of a palladium-gold catalyst and acetic acid produces vinyl acetate, which is a useful monomer for the polymer industry.
Acetoxylation is commonly performed by a vapor phase reaction using supported palladium-gold catalyst. Methods for supporting palladium-gold catalysts are also known. In general, the methods involve depositing a mixture of palladium and gold salts onto a support and then reducing the palladium and gold to metals.
Palladium and gold are both expensive precious metals. Therefore, many efforts have been made to increase the catalytic activity and reduce the amount of catalyst needed. For example, U.S. Pat. No. 6,022,823 teaches calcining the support impregnated with palladium and gold salts prior to reducing the metals. The catalyst shows improved activity.
Thus, it is still important to the chemical industry to find better ways to increase the catalytic activity of the supported palladium-gold catalysts. Ideally, the catalyst will have increased activity and require less precious metal.